The present invention relates to a control device for an automotive vehicle, and particularly to a control device which controls a rate of exhaust gas recirculated in accordance with the state of operation of an internal combustion engine.
The recirculation of exhaust gas in an internal combustion engine is effected in order to decrease the amount of oxides of nitrogen produced in the exhaust gas. A conventional device for this uses approximate values of functions of the engine load, such as the pressure difference between the upstream and downstream of a throttle valve, the vacuum in a carburetor venturi, etc, in order to control the opening degree of a valve which controls recirculation of the exhaust gas. In such a device, the recirculation of exhaust gas may be stopped when the temperature of cooling water for the engine is relatively low, and the characteristics of the recirculation during warm-up may be adjusted to the regulation of the flow rate of exhaust gas. However, it is difficult to obtain the correct ratio of exhaust gas recirculated for predetermined operational requirements by controlling the recirculation of exhaust gas using a small number of parameters and a small number of valve actuators because of economical problems. Further the recirculation of exhaust gas tends to be effected in operational regions in which the recirculation of exhaust gas is unnecessary. An increase in the number of the actuators and different sensors for precise control will increase the problems of manufacturing errors involved therein, which leads to unsatisfactory control and high manufacturing cost. If the specifications of the internal conbustion engine are changed, a great deal of effect and time is required for replacing and adjusting actuators.